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Unable to connect to the Serv-U server via File Explorer through FTP protocol

After upgrading Serv-U from an older version (e.g., 15.3.0) to the latest version (e.g., 15.5.4), users will encounter an FTP folder error when attempting to connect to the Serv-U FTP server via File Explorer.

First published date

5/27/2026 10:18 PM

Last published date

5/27/2026 10:42 PM

Overview

When connecting to the Serv-U FTP server via File Explorer using ftp://username:password@server, ftp://serv-u.com, or ftp://serverIP, user receives the following error message: 

 

Product section

Serv-U Managed File Transfer & Serv-U FTP Server

Cause

The “Require secure connection before login” setting is enabled in the Global or Domain level.

File Explorer only supports plain FTP. So when File Explorer initiates an FTP connection, it uses plain FTP only. Since Serv-U requires a secure connection (FTPS), the connection will not proceed.

Resolution

Disable the “Require secure connection before login” setting under Global > Limits & Settings > Limits > Limit Type > Connection or Domain > Limits & Settings > Limits > Limit Type > Connection.

 

Please Note:

Disabling the 'Require secure connection before login' option is a security risk that should be discussed and reviewed internally. 

Accessing FTP via File Explorer uses plain FTP rather than Secure FTP (Implicit or Explicit FTP).